Chock release column for use with expansible hole anchor

ABSTRACT

A chock release column operable for use with conventional hole anchor devices is provided and generally includes a cable cylinder operable for being secured about a load cable of an expansible hole anchor, a chock clearance portion extending from the cable cylinder that it corresponds in size and shape to an end of the center chock, and an enlarged head adapted for locating outside of a hole of a structure, the enlarged head generally defining a striking surface adapted for receiving a sudden force and transferring the force through the chock release column to a center chock or at least one side chock of the expansible hole anchor, such that the at least one side chock is movable from the anchor-expanding position to the anchor-contracting position to thereby dislodge said anchor from the hole of the structure.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/069,646, filed on Mar. 1, 2005, and entitled “EXPANSIBLEHOLE ANCHOR WITH ENLARGED CHOCK-RELEASING STRIKER HEAD,” which is acontinuation of and claims the benefit of priority of PCT/US04/24129,filed on Jul. 27, 2004, the content of all the aforesaid applicationsare relied upon and incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to safety devices and methodsfor fall protection, and more specifically, to safety devices including,in an exemplary embodiment, a chock release column operable for use withconventional expansible hole anchors.

2. Technical Background

In the construction industry, it is often necessary to provide fallprotection for workers or objects suspended at heights. Conventionally,expansible hole anchor bolts are used to meet these needs. Contractorstypically utilize the expansible hole anchors in the hopes that theyprovide a simple, reliable and relatively inexpensive means forconnecting a cable, rope or wire to a drilled hole in a hard material,that is easy to install in and remove from the hole, and thateffectively anchors to the hole while applying a minimum stress to thehole, while providing a minimum sensitivity to the angular orientationof the expansion bolt in the hole. However, substantial drawbacks andlimitations exist in conventional expansible hole anchors.

A first shortcoming of conventional hole anchors is that the handle isapplicable for moving the anchor from a normal expanded condition to acontracted condition for inserting and removing the anchor from thehole. In order to remove the anchor, the user is typically instructed tomanually retract the handle to disengage the anchor chocks from aninside wall of the hole. In many cases, the anchor is so tightly lodgedinside the hole that movement of the handle is difficult, if notimpossible. This occurs often, as the operating instructions call for atug on the load cable to set the anchor during insertion. Additionalforces exerted on the anchor caused by a worker movement, or during aworker's fall cause even greater locking engagement of the anchorchocks. The instructions commonly provided for dislodging an embeddedanchor are to insert a small, narrow flat screwdriver into the hole, andcreate an impact force on an end fitting to overcome the lockingfriction. In practice, this procedure is generally ineffective; oftenresulting in mangled or broken retraction cables, and rendering theanchor unsuitable for future use. This procedure further inconveniencesthe user by requiring the availability of special tools in order toaccess and release the anchor chocks. If all methods of removal fail,the exposed portion of the anchor is torched off, a new hole drilled,and the balance of the anchor is left in the old hole.

A further problem of conventional anchors relates to the exposure ofcontrol cables operable for moving the anchor from the expandedcondition to the contracted condition. Typically, these cables will beardirectly against an inside wall of the anchor hole, resulting insubstantial abrasion and chaffing when the anchor is inserted into andremoved from the hole. Further wear is created when the worker movesabout causing the control cables to grind against the concrete lip ofthe hole. If left undetected, the worn cables will eventually foul thecable motion and cause the anchor to fail which may result ininoperability, serious injury, or death.

A further problem with conventional hole anchors is the number ofcomponents required for assembly and use. Existing hole anchors requirea large number of parts which disadvantageously increase the complexityand cost of manufacture. In addition, conventional hole anchorsdisadvantageously have a striker head which may lose contact with thecenter chock, thus providing a defective unit.

Accordingly, it would be desirable to have an improved expansible holeanchor which overcomes the noted shortcomings of conventional devices.In one such solution, it would be desirable to provide an expansiblehole anchor which reduces the manufacturing costs and the complexity ofassembly. In other solutions, it would be desirable to provide anexpansible hole anchor with a chock releasing column which is securedabout a load cable and is operable for transmitting force to a centerchock, thereby dislodging the anchor from a hole. In still othersolutions, it would be desirable to provide an expansible hole anchorwith a chock releasing column which decreases side load forces which maybe applied to the center chock during use.

SUMMARY OF THE INVENTION

The present invention is designed to overcome the deficiencies andshortcomings of the devices described above. The present invention isdesigned to reduce the manufacturing costs and the complexity ofassembly. In all exemplary embodiments, the present invention relates toan improved expansible hole anchor with a chock releasing column whichis advantageously secured about a load cable of the hole anchor and isoperable for transmitting force to a center chock of the hole anchor,thereby dislodging the anchor from a hole. In all exemplary embodiments,the present invention advantageously provides an improved hole anchorwhich decreases side load forces which may be applied to the centerchock during use through the use of an improved chock release column.The present invention is easily installed and removed from a hole formedwith a solid structure. In one application, the present inventiondiscloses a chock release column for use with a conventional hole anchorthat is inserted into a hole drilled in a concrete wall at aconstruction site. A safety harness, lifeline, and other fall protectiongear is secured to the worker and to the anchor to arrest the worker inthe event of a fall. In another application, the present invention isdirected to a chock release column for use with a conventional holeanchor that is applicable for use in securing equipment, such asscaffolding, to a concrete structure, or as a lift connection point foritems with a suitable hole, such as preformed concrete or boulders, orfor use in recreational rock climbing.

According to an exemplary embodiment, a chock release column is providedfor use with a conventional, expansible anchor that is adapted forinsertion into a hole formed with a structure provided. The hole anchorgenerally includes a load cable, a center chock attached to an end ofsaid load cable, at least one, but preferably two, side chocks adjacentto said center chock and adapted for movement between ananchor-contracting position and an anchor-expanding position, whereby insaid anchor-contracting position, said anchor is readily inserted intoand removed from the hole of the structure, and in said anchor-expandingposition, said anchor is locked inside the hole of the structure, and achock release column secured about the load cable. In exemplaryembodiments, the chock release column generally includes an enlargedhead adapted for locating outside of the hole, said enlarged headdefining a striking surface adapted for receiving a sudden force andtransferring the force through said chock-release column to said centerchock or at least one side chock, such that said at least one side chockis movable from the anchor-expanding position to the anchor-contractingposition to thereby dislodge said anchor from the hole of the structure.

In exemplary embodiments, the chock release column is secured about aload cable such that it abuts the center chock. In other exemplaryembodiments, the chock release column is secured about the load cablesuch that it is spaced from the center chock. In such embodiments, forceapplied to the chock release column may be transmitted through the loadcable to the center chock, thereby dislodging the same from a hole. Thechock release column may be secured to the load cable by a fastener. Inother embodiments, the chock release column may be swaged to the loadcable. In exemplary embodiments, the chock release column may be held inposition by a positioning block.

In exemplary embodiments, the chock release column includes a chockclearance portion, a cable cylinder or shaft, and an enlarged head. Thechock clearance portion is configured such that it corresponds in sizeand shape to an end of the center chock. This configuration permits theside chock to translate along the center chock from an anchor expandingpotion to an anchor contracting position. At least one, but preferablytwo, cable guides are provided about the shaft.

Additional features and advantages of the invention will be set forth inthe detailed description which follows, and in part will be readilyapparent to those skilled in the art from that description or recognizedby practicing the invention as described herein, including the detaileddescription which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description present exemplary embodiments of theinvention, and are intended to provide an overview or framework forunderstanding the nature and character of the invention as it isclaimed. The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated into and constitutea part of this specification. The drawings illustrate variousembodiments of the invention, and together with the detaileddescription, serve to explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention are better understood when the following detailed descriptionof the invention is read with reference to the accompanying drawings, inwhich:

FIG. 1 is a side view of a chock release column constructed inaccordance with one exemplary embodiment of the present invention,wherein the chock release column is secured to a load cable of aconventional expansible hole anchor such that a space exists between thechock release column and the center chock;

FIG. 2 is perspective view of the hole anchor of FIG. 1;

FIG. 3 is a perspective view of the hole anchor of FIG. 1, wherein thecenter chock is provided with a cylindrical wedge type configuration andthe side chocks are provided with a corresponding shape which allows forsliding movement;

FIG. 4 is side view of a chock release column constructed in accordancewith another exemplary embodiment of the present invention, wherein thechock release column is secured to the load cable of a conventionalexpansible hole anchor such that is abuts the center chock; and

FIG. 5 is a perspective view of the hole anchor of FIG. 4.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings in which exemplary embodiments ofthe invention are shown. However, this invention may be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. These exemplary embodiments are providedso that this disclosure will be both thorough and complete, and willfully convey the scope of the invention to those skilled in the art.Like reference numbers refer to like elements throughout the variousdrawings. Further, as used in the description herein and throughout theclaims that follow, the meaning of “a”, “an”, and “the” includes pluralreference unless the context clearly dictates otherwise. Also, as usedin the description herein and throughout the claims that follow, themeaning of “in” includes “in” and “on” unless the context clearlydictates otherwise.

The present invention overcomes the shortcomings of conventional holeanchors by securing a chock release column of a hole anchor device abouta load cable such that it abuts a center chock or is operable fortransmitting force through the load cable to the center chock whendislodging the same from a hole is desired. This method of securing thechock release column and the center chock together reduces the overallcost and the number of components required for manufacture. Further, thepresent invention prevents the chock release column from defectivelylosing contact with the center chock and provides space for an ergonomicpivot handle to be used, while shortening the overall length of theunit. Still further, the chock release column of the present inventionadvantageously enters into the inside of the hole during use, thusdecreasing side loads which may be placed upon the center chock.

In exemplary embodiments of the present invention, an expansible holeanchor is provided which generally includes a load cable having a centerchock connected to one end and a loop at the opposite end, at least oneside chock abutting the outer surfaces of the center chock such thatthey may translate between an expanded position and a retractedposition, a handle interconnected to the at least one side chock by atleast one chock cable, a retractor spring to bias the at least one sidechock in the extended position, and a chock release column having anenlarged head and being interposed between the handle and the centerchock. In exemplary embodiments, the chock release column is secured toload cable such that it abuts the center chock. In other exemplaryembodiments, the chock release column is secured or swaged to the loadcable such that it is spaced apart from the center chock. In suchembodiments, the chock release column is operable for transmitting forceapplied thereto through the load cable to the center chock, therebydislodging the same from a hole.

In exemplary embodiments, the expansible hole anchor is generallyoperated by pulling back the handle which retracts the at least one sidechock, reducing the outside diameter over the combination of the centerchock and the at least one side chock. The anchor is then inserted intoa hole (in rock, concrete, etc.) and the handle is released. Springpressure causes the at least one side chock to translate along thecenter chock and expand to the hole diameter. When tension is placedupon the load cable, it pulls the center chock outward. The at least oneside chock tends to remain stationary because of friction between thehole and their outer surfaces. This, in turn, results in the centerchock being driven between the at least one side chock, expandinglaterally and increasing the outward gripping pressure. The greater theexternal load placed upon the anchor, the higher the gripping pressure.

To release the anchor, the handle is again retracted. This, in turn,retracts the at least one side chock to a diameter smaller than thehole. If the handle is stuck in position, an enlarged head of the chockrelease column, exposed outside the hole, may be pushed by hand orstruck with a hammer or other tool to dislodge the center chock andallow the at least one side chock to retract. The striking of theenlarged head transmits force through the load cable to, at least, thecenter chock or, in the alternative, transmits force directly to, atleast, the center chock.

Referring now specifically to the drawings, a conventional, expansiblehole anchor constructed in accordance with an exemplary embodiment ofthe present invention is illustrated in FIG. 1, and shown generally atreference numeral 10. The hole anchor 10 is adapted for insertion into ahole (not shown) formed with a solid structure, such as a concrete wall,and is applicable for use with safety harnesses, lifelines, and otherfall protection devices (not shown) worn by a worker to arrest theworker in the event of a fall. In exemplary embodiments, the anchor 10comprises a load cable 12 looped at one end 14 for attaching a safetydevice, and a center chock 16 located at an opposite end. It will beunderstood by those skilled in the art that the load cable 12 may becomprised of a steel wire. Further, it will be understood by thoseskilled in the art that any suitable material may be used. Stillfurther, it will be understood by those skilled in the art that the loadcable 12 may be a rod or rod like structure as opposed to a flexiblecable type structure. At least one side chock 18 is provided along thecenter chock 16 and cooperates, as described below, to constrict andexpand the anchor 10 relative to the hole of the structure. In theexemplary embodiments described herein two side chock are shown 18, 20for purposes of illustration only.

In exemplary embodiments and as best shown in FIGS. 1-2 and 4-5, thecenter chock 16 has a generally conically-shaped body. However, in otherexemplary embodiments, the center chock may be provided with acylindrical wedge type configuration 21 (FIG. 3). The side chocks 18 and20 reside adjacent the center chock 16, and have complementary profilesdesigned to provide maximum uniform gripping action when set inside thestructure hole. In exemplary embodiments, the outside surface of eachside chock 18 and 20 is preferably curved to conform to an inside wallof the structure hole, while the inside surface is convexly curved forsliding along an outside surface of the center chock 16. In otherexemplary embodiments, the inside surface of the side chocks 18 and 20may be provided with substantially planar surfaces that correspond andcooperate with the cylindrical wedge type configuration 21 of the centerchock 16, if the center chock 16 is provided with the wedgeconfiguration 21.

The side chocks 18 and 20, are attached to respective steel-wire,polymer, or composite chock cables 28 and 30. The chock cables 28, 30extend rearward to a spring-loaded handle 32. The handle 32 is carriedon the load cable 12, and is adapted for being manually retracted by theuser to move the side chocks 18, 20 from a normal anchor-expandingposition to an anchor-contracting position. In the anchor-contractingposition, the side chocks 18, 20 are more closely spaced apart onopposite sides of the center chock 16 such that the anchor 10 is readilyinserted into and removed from the hole of the structure. The rearportion of the center chock 16 has a relatively small diameter, therebyallowing substantial contraction of the anchor 10. Preferably, thesmallest section of the center chock 16 has a profile dimension justgreater than the diameter of the load cable 12. In the anchor-expandingposition, the side chocks 18, 20 are urged forward along diverging outersurfaces of the center chock 16. In use, the anchor 10 does not fullyexpand inside the hole, but instead forces the side chocks 18, 20 intosufficient frictional engagement with the inside wall of the structurehole to prevent inadvertent dislodging of the anchor 10. After insertingthe anchor 10 into the hole, the side chocks 18, 20 are set by onecontrolled pull on the cable loop 14.

Referring again to FIG. 1, a chock-release column 38 is carried on theload cable 12 adjacent the center chock 16, and comprises an integralcable cylinder 40, enlarged-diameter head 42 and a tapered, narrowed,stepped down, necked, or chock clearance portion 46. In other exemplaryembodiments, the chock release column 38 may comprise the cable cylinder40, the enlarged head 42 and the chock clearance portion 46 as separatecomponents, as opposed to integral ones. The chock release column 38 maybe secured or swaged to the load cable 12. Preferably, the chockclearance portion 46 of the chock release column 38 is sized and shapedto correspond to the size and shape (e.g., the diameter) of the centerchock end 17 nearest the column 38. By providing the chock clearanceportion 46 with a corresponding size and shape of the center chock end17, the side chocks 18, 20 may fully operate to an anchor expanding oranchor contracting position. In other exemplary embodiments (not shown),the chock release column 38 is comprised of a cable cylinder 40 whichcorresponds directly to the size and shape of the center chock end 17and an enlarged head 42. In such embodiments, the cable cylinder 40extends to the center chock end 17 or to a spaced portion 22 locatedbetween the center chock 16 and the chock release column 38.

In exemplary embodiments wherein the chock release column 38 is directlyswaged or fastened to the load cable 12 and spaced apart from the centerchock 16, a positioning block or spacer 50 is provided between theenlarged head 42 and the handle 32 such that the handle 32 remainscorrectly spaced from the column 38. In other exemplary embodiments, thehandle 32 may be provided with an extended portion (not shown) whichextends outwardly from the handle 32 to the enlarged head 42. In stillother exemplary embodiments wherein the chock release column 38 is notdirectly swaged or fastened to the load cable 12 and abuts the centerchock 16, a positioning block or spacer 50 is provided for holding thechock release column 38 in place. In turn, a ferrule stop 55 which isswaged about the load cable 12 is provided to maintain the spacer 50 inposition.

In use, the enlarged head 42 locates outside of the structure hole, anddefines a flat annular striking or bearing surface 44 designed toreceive a force applied using the thumbs or any rigid object, such as asnap hook. In exemplary embodiments, the chock release column 38 abutsthe center chock 16 such that the force is transferred directly throughthe chock-release column 38 to the center chock 16 to dislodge the sidechocks 18, 20 from friction-locking engagement inside the hole. In otherexemplary embodiments, the chock release column 38 is spaced apart fromthe center chock 16 such that the force is transmitted from the chockrelease column 38 through the spaced portion 22 of the load cable 12 tothe center chock 16 to dislodge the side chocks 18, 20. Once dislodged,the side chocks 18, 20 are easily retracted by the handle 32; movingfrom the anchor-expanding position to the anchor-contracting position toremove the anchor 10 from the structure hole.

In exemplary embodiments, the preferable maximum diameter of thestriking head 42 is greater than the maximum distance between the sidechocks 18 and 20 in the anchor-expanding condition. As such, uponinsertion of the anchor 10 into the hole, the enlarged striking head 42is pushed directly against the mouth of the hole, thereby locating theanchor chocks 16, 18 and 20 inside the hole in a position of maximumeffectiveness and safety, while maintaining ready access to the exposedstriking surface 44.

According to one embodiment, the enlarged head 42 of the chock-releasecolumn 38 has three openings for receiving the load cable 12 and chockcables 28, 30, respectively. Preferably, the center opening has aradiused edge to minimize wear on the load cable 12 when pulledvertically. A reduced diameter, integral neck 48 extends forward of theenlarged head 42 has interior passages or longitudinal exterior groovesto designed receive the chock cables 28, 30.

A retractor spring 54 is carried on the load cable 12 rearward of thehandle 32. The retractor spring 54 is compressed between the handle 32and cable loop 14, and operates to normally urge the handle 32 and chockcables 28, 30 forward thereby biasing the side chocks 18 and 20 in theanchor-expanding position. The retractor spring 54 is preferablypre-loaded in the anchor-expanding position at greater than 20% of itsmaximum compression force. Preferably, the cable loop 14 is secured by aduplex ferrule 56 and reinforced with a metal thimble (not shown). Instill other exemplary embodiments, one or more retractor springs may beplaced around at least one of the chock cables between the side chocksand the chock release column, or extending into recesses within thechock release column.

In some exemplary embodiments, the chock release column 38 may besecured to the load cable 12 such that the chock release column 38cannot translate or slide along the load cable 12. In other exemplaryembodiments, the chock release column 38 may be secured to the centerchock 16 by a fastener 80. It will be understood by those skilled in theart that the fastener 80 may be any suitable fastening device forsecuring the chock release column 38 to the center chock 16 including,but not limited to rivets, screws, nails, rods, ties, etc. The fastener80 may extend through a bore located in the cable cylinder 40 and mayextend at least partially into the load cable 12. Advantageously, thismanner of attachment permits the chock release column 38 to pivot aboutthe center chock 16, but not translate or slide. In other exemplaryembodiments, a pivot relief angle may be provided at the left edge ofthe chock release column 38. Further, this manner of attachment permitsthe use of a unit having a smaller overall length when compared toconventional hole anchors.

As illustrated in FIGS. 1, 2, 4, and 5 shows a center chock 16 having anouter surface including convex portions along with side chocks 18 and 20having complementary concave inner surfaces. Preferably, the surfaces16, 18 and 20 are each rotationally symmetric about the longitudinalaxis, and more preferably still, the surfaces of the center and sidechocks are complementarily shaped. An example of complementarily shapedcenter and outer chocks is shown in the FIGS. 1, 2, 4 and 5. Here, thecenter chock 16 is shaped as a frustum so that the surface is convex andthe side chock surfaces 18 and 20 are concave and substantially conformto the frustum. The reverse geometry may also be employed for thisexample, wherein the surfaces 18 and 20 are convex and shaped asportions of frustums, and the center chock surface 16 is concave andsubstantially conforms to these portions. Moreover, the surfaces 16, 18and 20 may include only portions that are complementarily frustoconicalwhere desired. Further still, as detailed above the center chock 16 mayhave a cylindrical wedge type configuration 21 (FIG. 3).

The complementarily shapes provide a preferred means for ensuringintimate conformance between the respective ramping surfaces of thecenter and side chocks over a range of relative linear movementtherebetween, wherein the force exerted between the chocks isdistributed over a maximum surface area. This increases reliability bydecreasing stress and wear, as well as increases hole-engaging strengthby permitting the aforementioned force to be maximized.

The embodiments described above provide advantages over conventionalexpansible hole anchors and associated methods of manufacture. It willbe apparent to those skilled in the art that various modifications andvariations can be made to the present invention without departing fromthe spirit and scope of the invention. Thus, it is intended that thepresent invention cover the modifications and variations of thisinvention provided they come within the scope of the appended claims andtheir equivalents. Furthermore, the foregoing description of thepreferred embodiment of the invention and best mode for practicing theinvention are provided for the purpose of illustration only and not forthe purpose of limitation—the invention being defined by the claims.

1. An expansible anchor adapted for inserting into a hole formed with astructure, said anchor comprising: a load cable; a center chock attachedto an end of said load cable; at least one side chock adjacent to saidcenter chock and adapted for movement between an anchor-contractingposition and an anchor-expanding position; a chock release column havinga cable cylinder portion and an enlarged head adapted for locatingoutside of the hole, said enlarged head defining a striking surfaceadapted for receiving a sudden force and transferring the force throughsaid chock-release column to said center chock, such that said at leastone side chock is movable from the anchor-expanding position to theanchor-contracting position to thereby dislodge said anchor from a holeof a structure; and a handle carried by said load cable and adapted formoving said at least one side chock from the anchor-expanding positionto the anchor-contracting position.
 2. The expansible hole anchor ofclaim 1, wherein the chock release column further comprises a chockclearance portion.
 3. The expansible hole anchor of claim 1, wherein thechock release column is swaged about the load cable.
 4. The expansiblehole anchor of claim 3, wherein the chock release column abuts thecenter chock.
 5. The expansible hole anchor of claim 3, wherein thechock release column is spaced apart from the center chock.
 6. Theexpansible hole anchor of claim 1, wherein the chock release column issecured to the load cable by a fastener.
 7. The expansible hole anchorof claim 6, wherein the chock release column abuts the center chock. 8.The expansible hole anchor of claim 6, wherein the chock release columnis spaced apart from the center chock.
 9. The expansible hole anchor ofclaim 2, wherein the chock clearance portion is corresponding in size toand end of the center chock which is nearest the chock release column.10. A chock release column operable for use with an expansible holeanchor, comprising: a cable cylinder portion; and an enlarged headadapted for locating outside of a hole, said enlarged head defining astriking surface adapted for receiving a sudden force and transferringthe force through said chock-release column to a center chock of theexpansible hole anchor, such that at least one side chock of theexpansible hole anchor is movable from the anchor-expanding position tothe anchor-contracting position to thereby dislodge said anchor from thehole.
 11. The chock release column of claim 10, wherein the chockrelease column further comprises a chock clearance portion.
 12. Thechock release column of claim 10, wherein the chock release column isswaged about a load cable of the expansible hole anchor.
 13. The chockrelease column of claim 12, wherein the chock release column abuts thecenter chock.
 14. The chock release column of claim 12, wherein thechock release column is spaced apart from the center chock.
 15. Thechock release column of claim 10, wherein the cable cylinder iscorresponding in size to and end of the center chock which is nearestthe chock release column.
 16. The chock release column of claim 11,wherein the chock clearance portion is corresponding in size to and endof the center chock which is nearest the chock release column.
 17. Thechock release column of claim 11, wherein the cable cylinder, theenlarged head and the chock clearance portion are integral inconstruction.
 18. The chock release column of claim 11, wherein thecable cylinder, the enlarged head and the chock clearance portion areseparate components joined together.
 19. A chock release columnsupported on a load cable of an expansible hole anchor, the chockrelease column comprising: a cable cylinder portion; and an enlargedhead defining a striking surface; and a chock clearance portion, saidchock clearance portion corresponding in size to and end of a centerchock of the expansible hole anchor which is nearest the chock releasecolumn.
 20. The chock release column of claim 19, wherein said strikingsurface of the enlarged head is adapted for receiving a sudden force andtransferring the force through the chock-release column to the centerchock, such that the expansible hole anchor is movable from theanchor-expanding position to the anchor-contracting position.